1. Field of the Invention
The present invention relates to a hatchback door structure for vehicles, which is fitted up on a tailgate of a vehicle.
2. Description of the Related Art
A hatchback door fitted up on a tailgate in a rear part of a vehicle is jointed to the vehicle with a hinge structure in general. An opening-closing motion of the hatchback door is performed by rotating the door about the hinge located at an upper end of the door. This type of the hatchback door is required to increase a rigidity for improving collision fracture strength and for avoiding muffled sounds when a vehicle runs on a punishing road. On the other hand, the hatchback door is required to be light for reducing fuel consumption of a vehicle and for improving easiness of the opening-closing motion of the door. Because of the above reasons, a hatchback door for vehicles has been known, in which a structure of the hatchback door is configured by combining two thin panels of an outer panel and an inner panel which has openings, and the structure is also reinforced by a beam and the like as needed (see Japanese Patent No. 3013921, Japanese Patent Laid-Open Publication Kokai No. H11-514613).
A hatchback door structure has been known, which includes an inner panel in which a lateral beam is integrally formed with a frame so that the lateral beam partitions the frame, which has a shape outlining an outer shape of the hatchback door, into an upper side and a bottom side.
FIG. 5 is a schematic view of an example of a conventional hatchback door structure seen from outside a vehicle. A hatchback door structure 101 of a vehicle V includes an inner panel 106 which is configured with a frame 109 and a lateral beam 118, and has a window glass 107 in an opening 112a which is defined by the frame 109 and the lateral beam 118 on the upper side of the lateral beam 118. In an opening 112b defined by the frame 109 and the lateral beam 118 on the bottom side of the lateral beam 118, a pair of connection reinforcements 100a are disposed. A lower end of each of the connection reinforcements 100a is welded on the frame 109 through a lock reinforcement 100b which is fixed to a bottom center of the frame 109. The connection reinforcements 100a extend in a V-shape to respective upper corners of the opening 112b. In addition, an upper end of each of the connection reinforcements 100a is welded on respective corner reinforcements 100c which are fixed on respective upper corners of the opening 112b. In the hatchback door structure 101, a rigidity of the inner panel 106 is increased by disposing the pair of connection reinforcements 100a in the opening 112b and fixing them to the frame 109.
However, in the aforementioned conventional hatchback door structure 101, the discrete connection reinforcements 100a are welded on the frame 109 and the lateral beam 118. In addition, discrete members of the lock reinforcement 100b and the corner reinforcements 100c are bonded on the frame 109 and the lateral beam 118 for fixing the reinforcements 100a. The hatch back door is required to have a high rigidity for reducing muffled sounds when a vehicle runs on a punishing road, while saving a weight for reducing fuel consumption of the vehicle and for enhancing easiness of an opening-closing motion of the door. In the aforementioned hatchback door structure 101, the rigidity is increased. However, the weight of the hatchback door is also increased. In addition, a manufacturing cost goes up due to increase in man-hours for welding the discrete members.
It is, therefore, an object of the present invention to provide a hatchback door structure which is light and sufficiently rigid, as well as capable of reducing a manufacturing cost.